Google Data APIs Patent License

We've always encouraged other developers to adopt Atom, the Atom Publishing Protocol, and the extensions that Google has created on top of those standards, but we realized the issue of patents may have held back some adopters. Well, those concerns end today as we are giving a no-charge, royalty-free license to any patents we have that you would need to implement Atom, AtomPub, or any of those extensions.

Hi Joe,
Interesting development but I'm confused. Can you explain which patents Google have that relate to the Atom or AtomPub specifications? Or to put it another way, ignoring any Google extensions, why would I need a royalty-free license to implement an Atom/AtomPub client or server?
Forgive my ignorance if I've missed something obvious...
Regards,
John.

John, I can't comment on Google's statement, but when IBM released a similar pledge last year, we had no known patents reading on Atom, but we felt the pledge was an important and helpful way of putting implementors at ease and encouraging implementation.